Lesson Seven: How Veterinarians and the U.S. Navy Marine Mammals Contribute to Conservation
Marine Mammal Hearing
Hearing is very important to marine mammals for communication, navigation, hunting prey, and avoiding predators. There is a lot of concern surrounding "noise pollution" in our oceans, or man-made sounds in the ocean that can affect marine mammals – either by altering their behavior after they hear the sound or damaging their hearing permanently. Although we know a lot about the hearing of some species of marine mammals, most species are considered "data deficient", even for basic information such as the frequency range that they are capable of hearing. This information is important, as scientists and conservationists need to know if the sounds being put into the ocean by humans are, in fact, heard by the marine mammals that live there and if the sound is damaging their hearing capabilities. Hearing can be tested in marine mammals by behavioral methods or by measuring brain waves produced in response to the hearing of a sound, which is called an auditory evoked potential (AEP). Veterinarians and scientists at the NMMF collaborate with the U.S. Navy Marine Mammal Program in the study of marine mammal hearing using both methods, as well as in the development of tools used for assessing hearing in marine mammals.
Medicine and Diagnostic Monitoring Tools
The veterinarians at the NMMF provide the utmost quality of care for the U.S. Navy's marine mammals. In doing so, we are able to develop tools to study the health of marine mammal populations around the globe.
Deepwater Horizon Oil Spill
After the 2010 Deepwater Horizon oil spill, the NMMF's veterinarians and scientists were called to the Gulf of Mexico to assess the health of the local dolphin population and impacts of the oil spill. Dr. Cynthia Smith and Dr. Forrest Gomez used enhanced ultrasound and other diagnostic techniques that were recently developed for the care of dolphins managed by the U.S. Navy. The NMMF Conservation Medicine team adapted the techniques and is now applying them in the field to evaluate reproductive health of wild populations. The veterinarians and scientists at the NMMF are also collaborating with veterinary and marine mammal experts to better understand other impacts of the Deepwater Horizon oil spill, including heart abnormalities, survival, abundance, reproduction rates, and their movements and distributions.
Photo: NMMF team conducts ultrasound on wild Bottlenose dolphin.
Vaquita Conservation
The NMMF is a key partner in VaquitaCPR (Conservation, Protection & Recovery), a consortium comprised of marine mammal scientists, veterinarians, and biologists from around the world who came together to attempt to save the world's most endangered marine mammal, the vaquita porpoise, from extinction. In 2017, the VaquitaCPR team set out on a bold rescue mission aimed at temporarily protecting vaquitas under human care until their natural habitat was safe for them to return.
Vaquitas have been drowning at alarming rates in gillnets for shrimp and finfish. The government of Mexico banned gillnet fisheries, but the vaquita porpoise continues to be a victim of bycatch due to illegal fishing for the totoaba. The swim bladders from the totoaba fish are highly valuable in Chinese markets. Along with the totoaba and masses of other marine life, vaquitas get entangled in these nets and drown. The vaquita porpoise can only be found in one place in the entire world – the Sea of Cortez in Baja, California in Mexico. As of 2021, it is estimated that there are about 10 vaquitas left in the entire world.
Protecting Killer Whales
Just as doctors keep your health records updated, NMMF biologists and veterinarians are working with our partners to track the condition of Southern Resident killer whales by creating a unique scientific health database. With these long-term records, researchers and managers can track individual whale health and determine how to best protect this endangered population of animals.
Saving Sea Lions
The NMMF participated in the response and investigation of several California sea lion unusual mortality events (UMEs). From 2013 to 2017, an unusually high number of malnourished California sea lion pups washed up on Southern California beaches. The dire situation led the U.S. National Oceanic and Atmospheric Administration (NOAA) to declare unusual mortality events. NMMF animal care experts provided support to Southern California marine mammal rescue facilities, as they faced an elevated number of patients. NMMF biologists and veterinarians supported NOAA's work to determine the specific cause of the UME. Scientists currently believe that changes in prey availability, especially sardines, an important nutritional source for nursing mother sea lions, led to the increased prevalence of starving, stranded, and dead young animals [4]